The present invention relates generally to missile autopilots, and more particularly, to blended missile autopilots comprising a direct lift missile autopilot employing canards or side thrusters and a tail-controlled autopilot.
A tactical missile accelerates normal to its velocity vector in order to maneuver and hit an intended target. Guidance algorithms are used to determine the desired acceleration. An autopilot is then commanded to deliver that acceleration. The term autopilot refers to software and hardware dedicated to delivering the missile acceleration commanded by the guidance algorithms.
The objective of autopilot design is to deliver commanded acceleration as accurately and quickly as possible. Acceleration can be generated aerodynamically via lift, or less commonly, via thrusters oriented normal to the missile longitudinal axis. Aerodynamic autopilots fall into four basic categories. These include tail controlled autopilots, autopilots having fixed tails with movable wing surfaces, canard controlled autopilots, and autopilots having a combination of movable tails and canards.
Tail controlled autopilots have movable control surfaces (tails) located at the aft end of the body of the missile, aft of the center of gravity. The tails are used to generate pitching moments. As the body is pitched, the resulting angle of attack generates body lift, providing the desired acceleration. Fixed wings may be used forward of the tails for improved lifting capabilities.
In an autopilot having fixed tails with movable wings, the wings are located near the missile center of gravity. The wings are pitched to directly generate lift, while the body remains at low angles of attack, generating little lift. The fixed tail surfaces provide pitching moments which tend to restore the body to zero angle-of-attack.
Canard controlled autopilots operate in a manner similar to tail controlled autopilots. The canards are mounted forward of the center of gravity, and are used to generate pitching moments, and angle-of-attack of the body of the missile. Fixed wings mounted aft of the canards are used to generate lift.
With direct lift autopilots employing both movable tails and canards, the pitching moments from forward mounted canards are balanced against the pitching moments of the aft mounted tails.
Each autopilot type has distinct advantages. Where high acceleration capability is needed, autopilots employing body lift (tail or canard control) are desirable since the body is capable of generating significantly more lift than relatively small, movable control surfaces, thrusters, or canards. Where very fast response time is required, direct lift autopilots are desirable, since the control surfaces or thrusters can generate lift much faster than the body of the missile, and thus generate lift more quickly.
With regard to other prior art, it is known that several Soviet missile designs employ movable tails and canards, but nothing is known about the autopilot designs used therein.
Accordingly, it is an objective of the present invention to provide for improved blended missile autopilots comprising a direct lift missile autopilot employing canards or side thrusters and a tail-controlled autopilot.